Lots of refactoring and improvements. Script hooks.

Can now establish and hold a session with BIRD, successfully detect Down
state, and call scripts on state change via an event dispatch engine.

Can't maintain a session with VyOS. I think it is calculating the timers
incorrectly, but don't trust my own implementation of course...

src/bfd.rs

@@ -0,0 +1,253 @@
+use std::{ffi::{OsStr, OsString}, fmt::{self, Display}, io::Cursor, ops::{Div, Mul}, time};
+
+use bytemuck::NoUninit;
+use byteorder::{BigEndian, WriteBytesExt};
+use nom::{bytes::complete::take, multi::many_m_n, number::complete::be_u8, IResult};
+use nom_derive::{NomBE, Parse};
+use proc_bitfield::*;
+
+#[repr(u8)]
+#[derive(ConvRaw, Debug, NomBE, PartialEq, Eq, Clone, Copy, NoUninit)]
+pub enum BfdDiagnostic {
+    None = 0,
+    TimeExpired = 1,
+    EchoFailed = 2,
+    NeighborDown = 3,
+    FwdPlaneReset = 4,
+    PathDown = 5,
+    ConcatPathDown = 6,
+    AdminDown = 7,
+    RevConcatPathDown = 8,
+    Reserved,
+}
+impl Display for BfdDiagnostic {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str(match self {
+            Self::None => "None",
+            Self::TimeExpired => "TimeExpired",
+            Self::EchoFailed => "EchoFailed",
+            Self::NeighborDown => "NeighborDown",
+            Self::FwdPlaneReset => "FwdPlaneReset",
+            Self::PathDown => "PathDown",
+            Self::ConcatPathDown => "ConcatPathDown",
+            Self::AdminDown => "AdminDown",
+            Self::RevConcatPathDown => "RevConcatPathDown",
+            Self::Reserved => "Reserved",
+        })
+    }
+}
+#[repr(u8)]
+#[derive(ConvRaw, Debug, NomBE, PartialEq, Eq, Default, Clone, Copy, NoUninit)]
+pub enum BfdState {
+    AdminDown = 0,
+    #[default]
+    Down = 1,
+    Init = 2,
+    Up = 3,
+}
+impl Display for BfdState {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(match self {
+            Self::AdminDown => "AdminDown",
+            Self::Down => "Down",
+            Self::Init => "Init",
+            Self::Up => "Up",
+        })
+    }
+}
+
+impl Into<&OsStr> for BfdState {
+    fn into(self) -> &'static OsStr {
+        match self {
+            Self::AdminDown => OsStr::new("AdminDown"),
+            Self::Init => OsStr::new("Init"),
+            Self::Down => OsStr::new("Down"),
+            Self::Up => OsStr::new("Up"),
+        }
+    }
+}
+
+#[repr(u8)]
+#[derive(ConvRaw, Debug, NomBE, PartialEq, Eq, Clone, Copy, NoUninit)]
+pub enum BfdAuthType {
+    None = 0,
+    SimplePassword = 1,
+    KeyedMD5 = 2,
+    MetKeyedMD5 = 3,
+    KeyedSHA1 = 4,
+    MetKeyedSHA1 = 5,
+    Reserved,
+}
+#[repr(transparent)]
+#[derive(Debug, NomBE, PartialEq, Eq, Clone, Copy, NoUninit, Hash)]
+pub struct BfdDiscriminator(pub u32);
+impl Display for BfdDiscriminator {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+#[repr(transparent)]
+#[derive(Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord, NoUninit, NomBE)]
+/// All intervals in BFD are specified in microseconds
+pub struct BfdInterval(u32);
+
+impl BfdInterval {
+    pub fn from_micros(micros: u32) -> Self {
+        Self(micros)
+    }
+    pub fn from_millis(millis: u32) -> Self {
+        Self(millis * 1000)
+    }
+    pub fn from_secs(secs: u32) -> Self {
+        Self(secs * 1000000)
+    }
+    pub fn from_secs_f32(secs: f32) -> Self {
+        Self((secs * 1000000.0) as u32)
+    }
+}
+
+impl From<BfdInterval> for time::Duration {
+    fn from(value: BfdInterval) -> Self {
+        time::Duration::from_micros(value.0 as u64)
+    }
+}
+impl From<time::Duration> for BfdInterval {
+    fn from(value: time::Duration) -> Self {
+        BfdInterval(value.as_micros() as u32)
+    }
+}
+impl Display for BfdInterval {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}us", self.0)
+    }
+}
+impl Mul<u32> for BfdInterval {
+    type Output = BfdInterval;
+    fn mul(self, rhs: u32) -> Self::Output {
+        BfdInterval(self.0 * rhs)
+    }
+}
+impl Mul<BfdInterval> for u32 {
+    type Output = BfdInterval;
+    fn mul(self, rhs: BfdInterval) -> Self::Output {
+        BfdInterval(self * rhs.0)
+    }
+}
+impl Div<u32> for BfdInterval {
+    type Output = BfdInterval;
+    fn div(self, rhs: u32) -> Self::Output {
+        BfdInterval(self.0 / rhs)
+    }
+}
+impl Div<BfdInterval> for u32 {
+    type Output = BfdInterval;
+    fn div(self, rhs: BfdInterval) -> Self::Output {
+        BfdInterval(self / rhs.0)
+    }
+}
+
+bitfield! {
+    #[derive(NomBE)]
+    pub struct BfdFlags(pub u32): Debug {
+        pub vers: u8 @ 29..=31,
+        pub diag: u8 [try_get BfdDiagnostic] @ 24..=28,
+        pub state: u8 [try_get BfdState] @ 22..=23,
+        pub poll: bool @ 21,
+        pub final_: bool @ 20,
+        pub cpi: bool @ 19,
+        pub auth_present: bool @ 18,
+        pub demand: bool @ 17,
+        pub multipoint: bool @ 16,
+        pub detect_mult: u8 @ 8..=15,
+        pub length: u8 @ 0..=7
+    }
+}
+
+#[derive(Debug)]
+pub struct BfdAuthSimplePassword(Vec<u8>);
+impl<'a> Parse<&'a [u8]> for BfdAuthSimplePassword {
+    fn parse(i: &'a [u8]) -> IResult<&'a [u8], Self, nom::error::Error<&'a [u8]>> {
+        let (i, res) = many_m_n(1, 16, be_u8)(i)?;
+        Ok((i, Self(res)))
+    }
+}
+
+#[derive(Debug, NomBE)]
+pub struct BfdAuthKeyedMD5 {
+    key_id: u8,
+    _reserved: u8,
+    seq: u32,
+    digest: [u8; 16],
+}
+
+#[derive(Debug, NomBE)]
+pub struct BfdAuthKeyedSHA1 {
+    key_id: u8,
+    _reserved: u8,
+    seq: u32,
+    hash: [u8; 20],
+}
+
+#[derive(Debug, NomBE)]
+#[nom(Selector = "BfdAuthType", Complete)]
+pub enum BfdAuthData {
+    #[nom(Selector = "BfdAuthType::SimplePassword")]
+    SimplePassword(BfdAuthSimplePassword),
+    #[nom(Selector = "BfdAuthType::KeyedMD5")]
+    KeyedMD5(BfdAuthKeyedMD5),
+    #[nom(Selector = "BfdAuthType::MetKeyedMD5")]
+    MetKeyedMD5(BfdAuthKeyedMD5),
+    #[nom(Selector = "BfdAuthType::KeyedSHA1")]
+    KeyedSHA1(BfdAuthKeyedSHA1),
+    #[nom(Selector = "BfdAuthType::MetKeyedSHA1")]
+    MetKeyedSHA1(BfdAuthKeyedSHA1),
+}
+
+impl BfdAuthData {
+    fn parse_be_with_length(
+        i: &[u8],
+        auth_type: BfdAuthType,
+        auth_len: u8,
+    ) -> IResult<&[u8], Self> {
+        let (new_i, data) = take(auth_len)(i)?;
+        let (_leftovers, retval) = BfdAuthData::parse_be(data, auth_type)?;
+        Ok((new_i, retval))
+    }
+}
+
+#[derive(Debug, NomBE)]
+pub struct BfdAuth {
+    auth_type: BfdAuthType,
+    auth_len: u8,
+    #[nom(Parse = "{ |i| BfdAuthData::parse_be_with_length(i, auth_type, auth_len) }")]
+    auth_data: BfdAuthData,
+}
+
+#[derive(Debug, NomBE)]
+pub struct BfdPacket {
+    pub flags: BfdFlags,
+    pub my_disc: BfdDiscriminator,
+    pub your_disc: BfdDiscriminator,
+    pub desired_min_tx: BfdInterval,
+    pub required_min_rx: BfdInterval,
+    pub required_min_echo_rx: BfdInterval,
+    #[nom(Cond = "flags.auth_present()")]
+    pub auth: Option<BfdAuth>,
+}
+
+impl BfdPacket {
+    pub fn serialize(&self) -> Result<Box<[u8]>, std::io::Error> {
+        // TODO: serialize auth
+        let buf = [0u8; 24];
+        let mut wtr = Cursor::new(buf);
+        wtr.write_u32::<BigEndian>(self.flags.0)?;
+        wtr.write_u32::<BigEndian>(self.my_disc.0)?;
+        wtr.write_u32::<BigEndian>(self.your_disc.0)?;
+        wtr.write_u32::<BigEndian>(self.desired_min_tx.0)?;
+        wtr.write_u32::<BigEndian>(self.required_min_rx.0)?;
+        wtr.write_u32::<BigEndian>(self.required_min_echo_rx.0)?;
+
+        Ok(Box::new(wtr.into_inner()))
+    }
+}

src/bin/rust-bfdd.rs

@@ -1,111 +1,43 @@
 use futures::future;
+use rust_bfd::events::{EventMessageSink, ScriptHookSink, StateChangeEvent};
+use rust_bfd::{set_ttl_or_hop_limit, BfdSessionStats};
+use rust_bfd::{bfd::*, events::EventMessage};
+use std::net::Ipv6Addr;
 use std::{
     collections::HashMap,
     error::Error,
-    fmt::{self, Display},
+    fmt::Display,
-    fs::read,
+    io::ErrorKind,
-    io::Cursor,
     mem::swap,
     net::{IpAddr, SocketAddr},
-    num::NonZeroU32,
-    pin::Pin,
     str::FromStr,
-    sync::{
+    sync::{atomic::Ordering, Arc},
-        atomic::{AtomicBool, Ordering},
+    time::{Duration, Instant},
-        Arc,
-    },
-    time::SystemTime,
 };
 
-use tokio::{
+// Necessary until a hop_limit method is added to UdpSocket
-    sync::{oneshot, Mutex},
+use nix::sys::socket::{setsockopt, sockopt};
-    time::{interval_at, Timeout},
+
-};
+use tokio::sync::{oneshot, Mutex};
 
-use byteorder::{BigEndian, WriteBytesExt};
 use env_logger::Env;
-use itertools::Itertools;
 use log::{debug, error, info, warn};
-use nom::{bytes::complete::take, multi::many_m_n, number::complete::be_u8, IResult};
+
-use nom_derive::{NomBE, Parse};
+use nom_derive::Parse;
-use proc_bitfield::*;
 use rand::prelude::*;
+use tokio::io;
+use tokio::net::UdpSocket;
+use tokio::sync::mpsc;
+use tokio::task::{self, JoinHandle};
 use tokio::time;
-use tokio::{io, join, task::JoinHandle};
-use tokio::{net::UdpSocket, sync::RwLock};
-use tokio::{sync::mpsc, time::Instant};
-use tokio::{task, time::Interval};
 
 use atomic::Atomic;
-use bytemuck::{NoUninit, Pod};
 
 const CONTROL_PORT: u16 = 3784;
 const ECHO_PORT: u16 = 3785;
 
 const ORDERING: Ordering = Ordering::Relaxed;
 
-#[repr(u8)]
-#[derive(ConvRaw, Debug, NomBE, PartialEq, Eq, Clone, Copy, NoUninit)]
-pub enum BfdDiagnostic {
-    None = 0,
-    TimeExpired = 1,
-    EchoFailed = 2,
-    NeighborDown = 3,
-    FwdPlaneReset = 4,
-    PathDown = 5,
-    ConcatPathDown = 6,
-    AdminDown = 7,
-    RevConcatPathDown = 8,
-    Reserved,
-}
-impl Display for BfdDiagnostic {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str(match self {
-            Self::None => "None",
-            Self::TimeExpired => "TimeExpired",
-            Self::EchoFailed => "EchoFailed",
-            Self::NeighborDown => "NeighborDown",
-            Self::FwdPlaneReset => "FwdPlaneReset",
-            Self::PathDown => "PathDown",
-            Self::ConcatPathDown => "ConcatPathDown",
-            Self::AdminDown => "AdminDown",
-            Self::RevConcatPathDown => "RevConcatPathDown",
-            Self::Reserved => "Reserved",
-        })
-    }
-}
-#[repr(u8)]
-#[derive(ConvRaw, Debug, NomBE, PartialEq, Eq, Default, Clone, Copy, NoUninit)]
-pub enum BfdState {
-    AdminDown = 0,
-    #[default]
-    Down = 1,
-    Init = 2,
-    Up = 3,
-}
-impl Display for BfdState {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.write_str(match self {
-            Self::AdminDown => "AdminDown",
-            Self::Down => "Down",
-            Self::Init => "Init",
-            Self::Up => "Up",
-        })
-    }
-}
-
-#[repr(u8)]
-#[derive(ConvRaw, Debug, NomBE, PartialEq, Eq, Clone, Copy, NoUninit)]
-pub enum BfdAuthType {
-    None = 0,
-    SimplePassword = 1,
-    KeyedMD5 = 2,
-    MetKeyedMD5 = 3,
-    KeyedSHA1 = 4,
-    MetKeyedSHA1 = 5,
-    Reserved,
-}
-
 #[derive(Debug)]
 pub enum BfdError {
     // field, value
@@ -122,134 +54,6 @@ impl Display for BfdError {
 }
 impl Error for BfdError {}
 
-#[repr(transparent)]
-#[derive(Debug, NomBE, PartialEq, Eq, Clone, Copy, NoUninit, Hash)]
-pub struct BfdDiscriminator(u32);
-impl Display for BfdDiscriminator {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        self.0.fmt(f)
-    }
-}
-
-#[repr(transparent)]
-#[derive(Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord, NoUninit, NomBE)]
-/// All intervals in BFD are specified in microseconds
-pub struct BfdInterval(u32);
-impl From<BfdInterval> for time::Duration {
-    fn from(value: BfdInterval) -> Self {
-        time::Duration::from_micros(value.0 as u64)
-    }
-}
-impl From<u32> for BfdInterval {
-    fn from(value: u32) -> Self {
-        BfdInterval(value)
-    }
-}
-bitfield! {
-    #[derive(NomBE)]
-    pub struct BfdFlags(pub u32): Debug {
-        pub vers: u8 @ 29..=31,
-        pub diag: u8 [try_get BfdDiagnostic] @ 24..=28,
-        pub state: u8 [try_get BfdState] @ 22..=23,
-        pub poll: bool @ 21,
-        pub final_: bool @ 20,
-        pub cpi: bool @ 19,
-        pub auth_present: bool @ 18,
-        pub demand: bool @ 17,
-        pub multipoint: bool @ 16,
-        pub detect_mult: u8 @ 8..=15,
-        pub length: u8 @ 0..=7
-    }
-}
-
-#[derive(Debug)]
-pub struct BfdAuthSimplePassword(Vec<u8>);
-impl<'a> Parse<&'a [u8]> for BfdAuthSimplePassword {
-    fn parse(i: &'a [u8]) -> IResult<&'a [u8], Self, nom::error::Error<&'a [u8]>> {
-        let (i, res) = many_m_n(1, 16, be_u8)(i)?;
-        Ok((i, Self(res)))
-    }
-}
-
-#[derive(Debug, NomBE)]
-pub struct BfdAuthKeyedMD5 {
-    key_id: u8,
-    _reserved: u8,
-    seq: u32,
-    digest: [u8; 16],
-}
-
-#[derive(Debug, NomBE)]
-pub struct BfdAuthKeyedSHA1 {
-    key_id: u8,
-    _reserved: u8,
-    seq: u32,
-    hash: [u8; 20],
-}
-
-#[derive(Debug, NomBE)]
-#[nom(Selector = "BfdAuthType", Complete)]
-pub enum BfdAuthData {
-    #[nom(Selector = "BfdAuthType::SimplePassword")]
-    SimplePassword(BfdAuthSimplePassword),
-    #[nom(Selector = "BfdAuthType::KeyedMD5")]
-    KeyedMD5(BfdAuthKeyedMD5),
-    #[nom(Selector = "BfdAuthType::MetKeyedMD5")]
-    MetKeyedMD5(BfdAuthKeyedMD5),
-    #[nom(Selector = "BfdAuthType::KeyedSHA1")]
-    KeyedSHA1(BfdAuthKeyedSHA1),
-    #[nom(Selector = "BfdAuthType::MetKeyedSHA1")]
-    MetKeyedSHA1(BfdAuthKeyedSHA1),
-}
-
-impl BfdAuthData {
-    fn parse_be_with_length(
-        i: &[u8],
-        auth_type: BfdAuthType,
-        auth_len: u8,
-    ) -> IResult<&[u8], Self> {
-        let (new_i, data) = take(auth_len)(i)?;
-        let (_leftovers, retval) = BfdAuthData::parse_be(data, auth_type)?;
-        Ok((new_i, retval))
-    }
-}
-
-#[derive(Debug, NomBE)]
-pub struct BfdAuth {
-    auth_type: BfdAuthType,
-    auth_len: u8,
-    #[nom(Parse = "{ |i| BfdAuthData::parse_be_with_length(i, auth_type, auth_len) }")]
-    auth_data: BfdAuthData,
-}
-
-#[derive(Debug, NomBE)]
-pub struct BfdPacket {
-    flags: BfdFlags,
-    my_disc: BfdDiscriminator,
-    your_disc: BfdDiscriminator,
-    desired_min_tx: BfdInterval,
-    required_min_rx: BfdInterval,
-    required_min_echo_rx: BfdInterval,
-    #[nom(Cond = "flags.auth_present()")]
-    auth: Option<BfdAuth>,
-}
-
-impl BfdPacket {
-    fn serialize(&self) -> Result<Box<[u8]>, std::io::Error> {
-        // TODO: serialize auth
-        let buf = [0u8; 24];
-        let mut wtr = Cursor::new(buf);
-        wtr.write_u32::<BigEndian>(self.flags.0)?;
-        wtr.write_u32::<BigEndian>(self.my_disc.0)?;
-        wtr.write_u32::<BigEndian>(self.your_disc.0)?;
-        wtr.write_u32::<BigEndian>(self.desired_min_tx.0)?;
-        wtr.write_u32::<BigEndian>(self.required_min_rx.0)?;
-        wtr.write_u32::<BigEndian>(self.required_min_echo_rx.0)?;
-
-        Ok(Box::new(wtr.into_inner()))
-    }
-}
-
 /// Data structure to store the state of the Bfd machine. The impl does *not*
 /// implement any Bfd logic, it is merely a thread-safe data structure
 #[derive(Debug)]
@@ -355,7 +159,7 @@ impl BfdSessionState {
         self.desired_min_tx_interval.load(ORDERING)
     }
     fn set_desired_min_tx_interval(&self, value: BfdInterval) {
-        self.desired_min_tx_interval.store(value, ORDERING)
+        self.desired_min_tx_interval.store(value, ORDERING);
     }
     fn required_min_rx_interval(&self) -> BfdInterval {
         self.required_min_rx_interval.load(ORDERING)
@@ -398,30 +202,9 @@ struct BfdSession {
     tx: mpsc::Sender<SessionControlCommand>,
     rx_watchdog: Option<mpsc::Sender<WatchdogReset>>,
     cur_interval: BfdInterval,
+    event_dispatcher: EventDispatcherHandle,
 }
 
-#[derive(Debug)]
-struct BfdSessionStats {
-    local_ip: IpAddr,
-    remote_ip: IpAddr,
-    local_discr: BfdDiscriminator,
-    remote_discr: BfdDiscriminator,
-    state: BfdState,
-    last_diag: BfdDiagnostic,
-    control_packets_rx: u64,
-    control_packets_tx: u64,
-    last_change: Instant,
-}
-impl Display for BfdSessionStats {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        writeln!(
-            f,
-            "{:<20} {:<9} {:>6} {:>6}",
-            self.remote_ip, self.state, self.control_packets_rx, self.control_packets_tx
-        )?;
-        write!(f, "  LD:{} RD:{} Diag:{} Last: {}s", self.local_discr, self.remote_discr, self.last_diag, Instant::now().duration_since(self.last_change).as_secs())
-    }
-}
 impl From<&BfdSessionState> for BfdSessionStats {
     fn from(state: &BfdSessionState) -> Self {
         Self {
@@ -434,6 +217,8 @@ impl From<&BfdSessionState> for BfdSessionStats {
             control_packets_rx: state.control_packets_rx(),
             control_packets_tx: state.control_packets_tx(),
             last_change: state.last_state_change(),
+            detect_time: state.detection_time(),
+            base_interval: BfdInterval::from_secs(0), // TODO: This is a hack and will be patched up in the session
         }
     }
 }
@@ -463,10 +248,16 @@ struct BfdSessionHandle {
 }
 
 impl BfdSessionHandle {
-    async fn new(local_addr: IpAddr, remote_addr: IpAddr, local_discr: BfdDiscriminator) -> Self {
+    async fn new(
+        local_addr: IpAddr,
+        remote_addr: IpAddr,
+        local_discr: BfdDiscriminator,
+        event_dispatcher: EventDispatcherHandle,
+    ) -> Self {
         let (tx, rx) = mpsc::channel(32);
         let new_self = Self { tx };
-        let periodic = BfdPeriodicSenderHandle::new(new_self.clone(), BfdInterval(1_000_000));
+        let periodic =
+            BfdPeriodicSenderHandle::new(new_self.clone(), time::Duration::from_secs(1).into());
 
         let mut session = BfdSession::new(
             rx,
@@ -475,6 +266,7 @@ impl BfdSessionHandle {
             local_addr,
             remote_addr,
             local_discr,
+            event_dispatcher,
         )
         .await;
         tokio::spawn(async move { session.run().await });
@@ -534,8 +326,8 @@ impl BfdPeriodicSender {
         }
     }
     async fn run(&mut self) {
-        let base_interval = time::Duration::from_micros(self.cur_interval.0 as u64 * 3 / 4);
+        let base_interval = self.cur_interval * 3 / 4;
-        let mut clock = time::interval(base_interval);
+        let mut clock = time::interval(base_interval.into());
         let mut running = true;
 
         loop {
@@ -560,7 +352,7 @@ impl BfdPeriodicSender {
                             ,
                             PeriodicControlCommand::Start => { debug!("Starting periodic packets"); running = true },
                             PeriodicControlCommand::SetMinInterval(i) => {
-                                let base_interval = time::Duration::from_micros(i.0 as u64 * 3 / 4);
+                                let base_interval: Duration = (i * 3 / 4).into();
                                 debug!("Updating base interval to {}ms (jittering {} to {}ms)", base_interval.as_millis(), base_interval.as_millis(), base_interval.as_millis() + base_interval.as_millis() / 3);
                                 clock = time::interval_at(
                                     time::Instant::now() + base_interval.into(),
@@ -586,6 +378,7 @@ impl BfdSession {
         local_addr: IpAddr,
         remote_addr: IpAddr,
         local_discr: BfdDiscriminator,
+        event_dispatcher: EventDispatcherHandle,
     ) -> Self {
         let mut rng = rand::thread_rng();
 
@@ -594,7 +387,7 @@ impl BfdSession {
         let control_sock = UdpSocket::bind(SocketAddr::new(local_addr, source_port))
             .await
             .unwrap();
-        control_sock.set_ttl(255).unwrap();
+        set_ttl_or_hop_limit(&control_sock, 255).unwrap();
         // control_sock
         //     .connect(SocketAddr::new(remote_addr, CONTROL_PORT))
         //     .await?;
@@ -605,7 +398,8 @@ impl BfdSession {
             tx,
             periodic,
             rx_watchdog: None,
-            cur_interval: BfdInterval(1_000_000),
+            cur_interval: BfdInterval::from_secs(1),
+            event_dispatcher,
             state: BfdSessionState {
                 control_sock: Arc::new(control_sock),
                 peer_addr: remote_addr,
@@ -614,9 +408,9 @@ impl BfdSession {
                 local_discr,
                 remote_discr: Atomic::new(BfdDiscriminator(0)),
                 local_diag: Atomic::new(BfdDiagnostic::None),
-                desired_min_tx_interval: Atomic::new(BfdInterval(1_000_000)),
+                desired_min_tx_interval: Atomic::new(BfdInterval::from_millis(300)),
-                required_min_rx_interval: Atomic::new(BfdInterval(300_000)),
+                required_min_rx_interval: Atomic::new(BfdInterval::from_millis(300)),
-                remote_min_rx_interval: Atomic::new(BfdInterval(1)),
+                remote_min_rx_interval: Atomic::new(BfdInterval::from_millis(300)),
                 demand_mode: Atomic::new(false),
                 remote_demand_mode: Atomic::new(false),
                 detect_mult: Atomic::new(3),
@@ -624,7 +418,7 @@ impl BfdSession {
                 rcv_auth_seq: Atomic::new(0),
                 xmit_auth_seq: Atomic::new(rng.gen()),
                 auth_seq_known: Atomic::new(false),
-                detection_time: Atomic::new(BfdInterval(0)),
+                detection_time: Atomic::new(BfdInterval::from_secs(0)),
                 poll_mode: Atomic::new(false),
 
                 control_packets_rx: Atomic::new(0),
@@ -639,6 +433,16 @@ impl BfdSession {
         if self.state.session_state() == new_state {
             return;
         };
+        self.event_dispatcher
+            .dispatch(EventMessage::StateChange(StateChangeEvent {
+                local_discr: self.state.local_discr(),
+                remote_discr: self.state.remote_discr(),
+                local_ip: self.state.control_sock().local_addr().unwrap().ip(), //TODO: shouldn't unwrap here, it will crash the program
+                remote_ip: self.state.peer_addr(),
+                from_state: self.state.session_state(),
+                to_state: new_state,
+            }))
+            .await;
         info!(
             "Peer {} state change {} -> {}",
             self.state.peer_addr(),
@@ -655,10 +459,20 @@ impl BfdSession {
                         .send(WatchdogReset::Terminate)
                         .await
                         .unwrap();
-                }
+                };
+                //   When bfd.SessionState is not Up, the system MUST set bfd.DesiredMinTxInterval to a value of not
+                //    less than one second (1,000,000 microseconds).  This is intended to ensure that the bandwidth
+                //    consumed by BFD sessions that are not Up is negligible, particularly in the case where a neighbor
+                //    may not be running BFD.
+                self.state.set_desired_min_tx_interval(std::cmp::min(
+                    self.state.desired_min_tx_interval(),
+                    BfdInterval::from_secs(1),
+                ));
+                self.update_transmit_interval().await;
             }
             (BfdState::AdminDown | BfdState::Down | BfdState::Init, BfdState::Up) => {
                 self.start_watchdog().await;
+                self.state.set_local_diag(BfdDiagnostic::None); // This doesn't seem to be required by the spec but seems sensible and at least FRR does it.
             }
             _ => {}
         }
@@ -673,7 +487,9 @@ impl BfdSession {
                     self.receive_control_packet(&packet).await;
                 }
                 SessionControlCommand::GetSessionStats { respond_to } => {
-                    respond_to.send(BfdSessionStats::from(&self.state)).unwrap()
+                    let mut stats =
+                        BfdSessionStats::from(&self.state).with_base_interval(self.cur_interval);
+                    respond_to.send(stats).unwrap()
                 }
                 SessionControlCommand::TxControlPacket { poll_response } => {
                     self.transmit_control_packet(poll_response).await
@@ -710,20 +526,28 @@ impl BfdSession {
             your_disc: self.state.remote_discr(),
             desired_min_tx: self.state.desired_min_tx_interval(),
             required_min_rx: self.state.required_min_rx_interval(),
-            required_min_echo_rx: BfdInterval(0),
+            required_min_echo_rx: BfdInterval::from_secs(0),
             auth: None,
         };
         let socket = self.state.control_sock.clone();
         let dest = self.state.peer_addr;
         self.state.control_packets_tx.fetch_add(1, ORDERING);
         debug!("tx packet: {:?}", packet);
-        socket
+        match socket
             .send_to(
                 packet.serialize().unwrap().as_ref(),
                 SocketAddr::new(dest, CONTROL_PORT),
             )
             .await
-            .unwrap();
+        {
+            Err(e) => {
+                warn!(
+                    "Error sending packet to {:?}:{} ({:?})",
+                    dest, CONTROL_PORT, e
+                );
+            }
+            Ok(_) => {}
+        }
     }
 
     async fn start_watchdog(&mut self) {
@@ -760,7 +584,10 @@ impl BfdSession {
         let mut temporary = Some(tx);
         swap(&mut temporary, &mut self.rx_watchdog);
         if temporary.is_some() {
-            debug!("Updating old watchdog with new detection time");
+            debug!(
+                "Updating old watchdog with new detection time ({}ms)",
+                duration.as_millis()
+            );
             temporary
                 .as_mut()
                 .unwrap()
@@ -879,7 +706,7 @@ impl BfdSession {
         self.state.set_last_remote_diag(p.flags.diag().unwrap());
 
         // If the Required Min Echo RX Interval field is zero, the transmission of Echo packets, if any, MUST cease.
-        if p.required_min_echo_rx == BfdInterval(0) {
+        if p.required_min_echo_rx == BfdInterval::from_secs(0) {
             // TODO: implement echo thread
         }
         // If a Poll Sequence is being transmitted by the local system and the Final (F) bit in the received packet is
@@ -987,15 +814,14 @@ impl BfdSession {
         let old = self.state.detection_time();
         self.state.set_detection_time(if !self.state.demand_mode() {
             (p.flags.detect_mult() as u32
-                * std::cmp::max(self.state.required_min_rx_interval(), p.desired_min_tx).0)
+                * std::cmp::max(self.state.required_min_rx_interval(), p.desired_min_tx))
             .into()
         } else {
             (self.state.detect_mult() as u32
                 * std::cmp::max(
                     self.state.desired_min_tx_interval(),
                     self.state.remote_min_rx_interval(),
-                )
+                ))
-                .0)
             .into()
         });
         if old != self.state.detection_time() {
@@ -1004,57 +830,172 @@ impl BfdSession {
     }
 }
 
-#[tokio::main]
+#[derive(Debug)]
-async fn main() -> io::Result<()> {
+enum EventDispatcherCommand {
-    env_logger::Builder::from_env(Env::default().default_filter_or("info")).init();
+    AddSink(Box<dyn EventMessageSink>),
-
+    DispatchMessage(EventMessage),
-    info!("rust-bfd starting up");
-
-    let local = SocketAddr::from_str("192.168.122.1:3784").unwrap();
-    let peers = vec![SocketAddr::from_str("192.168.122.132:3784").unwrap()];
-    let mut rng = rand::thread_rng();
-    let mut sessions_by_ip = HashMap::new();
-    let mut sessions_by_discr = HashMap::new();
-
-    for peer in peers {
-        let mut local_discr = BfdDiscriminator(0);
-        while local_discr.0 == 0 || sessions_by_discr.get(&local_discr).is_some() {
-            local_discr = BfdDiscriminator(rng.gen());
 }
-        let session = BfdSessionHandle::new(local.ip(), peer.ip(), local_discr).await;
 
-        sessions_by_ip.insert((local.ip(), peer.ip()), local_discr);
+struct EventDispatcher {
-        sessions_by_discr.insert(local_discr, session);
+    event_sinks: Vec<mpsc::Sender<EventMessage>>,
+    event_sink_handles: Vec<JoinHandle<()>>,
+    tx: mpsc::Sender<EventDispatcherCommand>,
+    rx: mpsc::Receiver<EventDispatcherCommand>, // TODO: there must be a better way to do this
 }
+
+impl EventDispatcher {
+    fn new(
+        channel_tx: mpsc::Sender<EventDispatcherCommand>,
+        channel_rx: mpsc::Receiver<EventDispatcherCommand>,
+    ) -> Self {
+        let event_sinks = Vec::new();
+        let event_sink_handles = Vec::new();
+
+        Self {
+            event_sinks,
+            event_sink_handles,
+            tx: channel_tx,
+            rx: channel_rx,
+        }
+    }
+    fn add_sink(&mut self, sink: Box<dyn EventMessageSink>) {
+        // Save the transmit channel
+        self.event_sinks.push(sink.channel());
+        // Run the sink
+        self.event_sink_handles.push(sink.run());
+    }
+    async fn dispatch(&self, event: EventMessage) {
         debug!(
-        "configured sessions: {}",
+            "EventDispatcher dispatching event {:?} to sinks {:?}",
-        future::join_all(
+            event, self.event_sinks
-            sessions_by_discr
-                .values()
-                .map(|session| async { session.get_stats().await.unwrap().to_string() })
-        )
-        .await
-        .join("\n\t")
         );
+        for sink in &self.event_sinks {
+            sink.send(event.clone()).await.unwrap();
+        }
+    }
+    async fn run(mut self) {
+        info!("Event dispatcher running");
+        while let Some(cmd) = self.rx.recv().await {
+            debug!("EventDispatcher got command {:?}", cmd);
+            match cmd {
+                EventDispatcherCommand::AddSink(sink) => self.add_sink(sink),
+                EventDispatcherCommand::DispatchMessage(event) => self.dispatch(event).await,
+            }
+        }
+    }
+}
 
-    let control_sock = Arc::new(UdpSocket::bind(local).await?);
+#[derive(Clone)]
+struct EventDispatcherHandle {
+    channel_tx: mpsc::Sender<EventDispatcherCommand>,
+}
+
+impl EventDispatcherHandle {
+    async fn new() -> Self {
+        let (channel_tx, channel_rx) = mpsc::channel(16);
+        let dispatcher = EventDispatcher::new(channel_tx.clone(), channel_rx);
+        tokio::spawn(async move { dispatcher.run().await });
+        Self { channel_tx }
+    }
+    async fn dispatch(&self, event: EventMessage) {
+        self.channel_tx
+            .send(EventDispatcherCommand::DispatchMessage(event))
+            .await
+            .unwrap();
+    }
+    async fn add_sink(&self, sink: Box<dyn EventMessageSink>) {
+        self.channel_tx
+            .send(EventDispatcherCommand::AddSink(sink))
+            .await
+            .unwrap()
+    }
+}
+
+struct Bfdd {
+    local: SocketAddr,
+    peers: Vec<SocketAddr>,
+    sessions_by_ip: HashMap<(IpAddr, IpAddr), BfdDiscriminator>,
+    sessions_by_discr: HashMap<BfdDiscriminator, BfdSessionHandle>,
+
+    control_socket: Arc<UdpSocket>,
+
+    event_dispatcher: EventDispatcherHandle,
+}
+
+impl Bfdd {
+    async fn new() -> Result<Self, Box<dyn Error>> {
+        // let local = SocketAddr::from_str("192.168.255.2:3784").unwrap();
+        let local = SocketAddr::new(Ipv6Addr::from_str("2001:db8::2").unwrap().into(), 3784);
+        let peers = vec![
+            // SocketAddr::from_str("192.168.122.132:3784").unwrap(),
+            // SocketAddr::from_str("192.168.255.1:3784").unwrap(),
+            SocketAddr::new(Ipv6Addr::from_str("2001:db8::1").unwrap().into(), 3784),
+        ];
+        let sessions_by_ip = HashMap::new();
+        let sessions_by_discr = HashMap::new();
+
+        // TODO: Bind only the sockets we need for the configuration, including multihop and run them in different tasks.
+        info!("Binding on {:?}", local);
+        let control_socket = Arc::new(UdpSocket::bind(local).await?);
         // If BFD authentication is not in use on a session, all BFD Control packets for the session MUST be sent with a
         // Time to Live (TTL) or Hop Limit value of 255.
-    control_sock.set_ttl(255).unwrap();
+        set_ttl_or_hop_limit(&control_socket, 255)?;
         let echo_socket = Arc::new(UdpSocket::bind(SocketAddr::new(local.ip(), ECHO_PORT)).await?);
 
-    let rx_thread = task::spawn(async move {
+        let event_dispatcher = EventDispatcherHandle::new().await;
-        let mut buf = [0; 1024];
+        event_dispatcher
-        loop {
+            .add_sink(Box::new(ScriptHookSink::new()))
-            // TODO: All received BFD Control packets that are demultiplexed to the session MUST be discarded if the
+            .await;
-            // received TTL or Hop Limit is not equal to 255. Need raw sockets for this.
+
-            let (len, addr) = control_sock.recv_from(&mut buf).await.unwrap(); // TODO: fallibility?
+        Ok(Self {
-            if let Ok((_leftover, packet)) = BfdPacket::parse(buf.as_slice()) {
+            local,
-                debug!("rx packet: {:?}", packet);
+            peers,
+            sessions_by_ip,
+            sessions_by_discr,
+            control_socket,
+            event_dispatcher,
+        })
+    }
+    async fn start_peers(&mut self) {
+        let mut rng = rand::thread_rng();
+        for peer in &self.peers {
+            let mut local_discr = BfdDiscriminator(0);
+            while local_discr.0 == 0 || self.sessions_by_discr.get(&local_discr).is_some() {
+                local_discr = BfdDiscriminator(rng.gen());
+            }
+            let session = BfdSessionHandle::new(
+                self.local.ip(),
+                peer.ip(),
+                local_discr,
+                self.event_dispatcher.clone(),
+            )
+            .await;
+
+            self.sessions_by_ip
+                .insert((self.local.ip(), peer.ip()), local_discr);
+            self.sessions_by_discr.insert(local_discr, session);
+        }
+    }
+    fn session_for_packet(
+        &self,
+        addr: &SocketAddr,
+        packet: &BfdPacket,
+    ) -> Option<&BfdSessionHandle> {
+        // Try to find a configured session for the remote IP if it doesn't send our discriminator, otherwise
+        // use the discriminator that was sent.
+
+        // https://datatracker.ietf.org/doc/html/rfc5880#section-6.3
+        //
+        // Once the remote end echoes back the local discriminator, all further received packets are
+        // demultiplexed based on the Your Discriminator field only (which means that, among other things, the
+        // source address field can change or the interface over which the packets are received can change, but
+        // the packets will still be associated with the proper session).
         let our_disc = if packet.your_disc == BfdDiscriminator(0) {
-                    if let Some(discr) =
+            if let Some(discr) = self
-                        sessions_by_ip.get(&(control_sock.local_addr().unwrap().ip(), addr.ip()))
+                .sessions_by_ip
+                .get(&(self.control_socket.local_addr().unwrap().ip(), addr.ip()))
             {
+                // TODO: Probably we should destroy the old session here?
                 debug!(
                     "Found session for unknown discriminator from {}: {}",
                     addr.ip(),
@@ -1063,41 +1004,83 @@ async fn main() -> io::Result<()> {
                 discr
             } else {
                 warn!("Unable to match packet to session with {}", addr.ip());
-                        continue;
+                return None;
             }
         } else {
             &packet.your_disc
         };
-                if let Some(session) = sessions_by_discr.get(our_disc) {
+        self.sessions_by_discr.get(our_disc)
+    }
+    async fn rx_packet(&self, addr: SocketAddr, packet: BfdPacket) {
+        if let Some(session) = self.session_for_packet(&addr, &packet) {
             session
                 .tx
                 .send(SessionControlCommand::RxPacket(packet))
                 .await
                 .unwrap();
         } else {
-                    warn!("Unable to match packet to session with {}", our_disc);
+            warn!("Unable to match packet to session with");
-                    continue;
+            return;
         }
-            } else {
-                warn!("Failed to parse packet");
     }
-
+    async fn run(mut self) -> io::Result<()> {
-            debug!(
+        info!("rust-bfd starting up");
+        self.start_peers().await;
+        info!(
             "configured sessions: {}",
             future::join_all(
-                    sessions_by_discr
+                self.sessions_by_discr
                     .values()
                     .map(|session| async { session.get_stats().await.unwrap().to_string() })
             )
             .await
             .join("\n\t")
         );
+
+        let rx_task =
+            task::spawn(async move {
+                let mut buf = [0; 1024];
+                loop {
+                    // TODO: All received BFD Control packets that are demultiplexed to the session MUST be discarded if
+                    // the received TTL or Hop Limit is not equal to 255. Need raw sockets for this.
+                    //
+                    // TODO: Maybe it is okay to receive in the session-specific socket instead of this global one? But
+                    // the RFC mentions that we must demux based on discriminator only.
+                    let (len, addr) = self.control_socket.recv_from(&mut buf).await.unwrap(); // TODO: fallibility?
+                    if let Ok((_leftover, packet)) = BfdPacket::parse(&buf[..len]) {
+                        debug!("rx packet ({:?}): {:?}", addr.ip(), packet);
+                        self.rx_packet(addr, packet).await
+                    } else {
+                        warn!("Failed to parse packet");
+                    }
+
+                    info!(
+                        "configured sessions: {}",
+                        future::join_all(self.sessions_by_discr.values().map(|session| async {
+                            session.get_stats().await.unwrap().to_string()
+                        }))
+                        .await
+                        .join("\n\t")
+                    );
                 }
             });
 
-    tokio::join!(rx_thread)
+        tokio::join!(rx_task)
             .0
             .expect("Unable to join on the receive thread");
 
         Ok(())
     }
+}
+
+#[tokio::main]
+async fn main() -> io::Result<()> {
+    env_logger::Builder::from_env(Env::default().default_filter_or("info"))
+        .format_timestamp_micros()
+        .init();
+
+    match Bfdd::new().await {
+        Ok(bfdd) => bfdd.run().await,
+        Err(e) => Err(std::io::Error::new(ErrorKind::Other, e.to_string())),
+    }
+}

src/events.rs

@@ -0,0 +1,171 @@
+use core::{fmt, str};
+use std::{
+    ffi::{OsStr, OsString},
+    net::IpAddr,
+    path::PathBuf,
+    process::ExitStatus,
+};
+
+use itertools::Itertools;
+use log::{debug, info, warn};
+use nix::unistd::{self, eaccess};
+use tokio::{
+    fs, process,
+    sync::mpsc,
+    task::{self, JoinHandle},
+};
+
+use crate::{BfdDiscriminator, BfdState};
+
+#[derive(Debug, Clone)]
+pub enum EventMessage {
+    StateChange(StateChangeEvent),
+}
+
+#[derive(Debug, Clone)]
+pub struct StateChangeEvent {
+    pub local_discr: BfdDiscriminator,
+    pub remote_discr: BfdDiscriminator,
+    pub local_ip: IpAddr,
+    pub remote_ip: IpAddr,
+    pub from_state: BfdState,
+    pub to_state: BfdState,
+}
+
+pub trait EventMessageSink: Send + Sync + fmt::Debug {
+    fn channel(&self) -> mpsc::Sender<EventMessage>;
+    fn run(self: Box<Self>) -> JoinHandle<()>;
+}
+
+#[derive(Debug)]
+pub struct ScriptHookSink {
+    script_dir: PathBuf,
+    tx_channel: mpsc::Sender<EventMessage>,
+    rx_channel: mpsc::Receiver<EventMessage>,
+}
+
+impl EventMessageSink for ScriptHookSink {
+    fn channel(&self) -> mpsc::Sender<EventMessage> {
+        self.tx_channel.clone()
+    }
+    fn run(self: Box<Self>) -> JoinHandle<()> {
+        task::spawn(async move { self.event_loop().await })
+    }
+}
+
+impl ScriptHookSink {
+    pub fn new() -> Self {
+        let (tx_channel, rx_channel) = mpsc::channel(16);
+        Self {
+            script_dir: "/etc/rust-bfd/hooks.d/".into(),
+            tx_channel,
+            rx_channel,
+        }
+    }
+    async fn script_runner<S: AsRef<OsStr>>(script_path: S, args: &[S], environment: &[(S, S)]) {
+        let mut cmd = process::Command::new("sh");
+        cmd.env_clear()
+            .arg0(&script_path)
+            .arg(&script_path)
+            .args(args)
+            .envs(environment.iter().map(|(k, v)| (k, v)));
+        debug!("Running command {:?}", cmd);
+        let result = cmd.output().await;
+        match result {
+            Ok(output) => {
+                info!(
+                    "Script `{} {}` completed with status {}",
+                    cmd.as_std().get_program().to_string_lossy(),
+                    cmd.as_std()
+                        .get_args()
+                        .map(|arg| arg.to_string_lossy())
+                        .join(" "),
+                    output.status
+                );
+                if !output.status.success() {
+                    if output.stdout.len() > 0 {
+                        warn!(
+                            " stdout: \n{}",
+                            str::from_utf8(output.stdout.as_slice()).unwrap()
+                        );
+                    }
+                    if output.stderr.len() > 0 {
+                        warn!(
+                            " stderr: \n{}",
+                            str::from_utf8(output.stderr.as_slice()).unwrap()
+                        );
+                    }
+                }
+            }
+            Err(e) => {
+                warn!("Failed to execute {:?}, {}", cmd, e);
+            }
+        }
+    }
+    async fn send_state_change(&self, event: &StateChangeEvent) {
+        debug!("Got a state change event! {:?}, running scripts", event);
+        let mut files = match fs::read_dir(&self.script_dir).await {
+            Ok(files) => files,
+            Err(e) => {
+                warn!(
+                    "Error opening script directory `{}` ({}), no hooks executed.",
+                    self.script_dir.as_os_str().to_string_lossy(),
+                    e
+                );
+                return;
+            }
+        };
+        let mut scripts = Vec::new();
+        while let Ok(Some(direntry)) = files.next_entry().await {
+            // Check if entry is a file
+            if direntry.file_type().await.is_ok_and(|ft| ft.is_file()) {
+                // Check if it's executable
+                let path = direntry.path();
+                if unistd::eaccess(&path, unistd::AccessFlags::X_OK).is_ok() {
+                    // Add to scripts array
+                    scripts.push(path);
+                }
+            }
+        }
+        // Execute in lexicographic order, so sort the list of found scripts
+        scripts.sort_unstable_by_key(|path| {
+            path.file_name()
+                .map_or(OsString::new(), |file| file.to_owned())
+        });
+
+        if scripts.len() > 0 {
+            // Build context
+            let mut args = Vec::<&OsStr>::new();
+            let mut env = Vec::<(&OsStr, &OsStr)>::new();
+
+            let remote_ip_str = OsString::from(event.remote_ip.to_string());
+            let local_ip_str = OsString::from(event.local_ip.to_string());
+            let remote_discr_str = OsString::from(event.remote_discr.to_string());
+            let local_discr_str = OsString::from(event.local_discr.to_string());
+
+            args.push(event.to_state.into());
+            args.push(&remote_ip_str);
+            env.push((OsStr::new("BFD_LAST_STATE"), event.from_state.into()));
+            env.push((OsStr::new("BFD_STATE"), event.to_state.into()));
+            env.push((OsStr::new("BFD_LOCAL_ADDR"), &local_ip_str));
+            env.push((OsStr::new("BFD_PEER_ADDR"), &remote_ip_str));
+            env.push((OsStr::new("BFD_LOCAL_DISCRIMINATOR"), &local_discr_str));
+            env.push((OsStr::new("BFD_PEER_DISCRIMINATOR"), &remote_discr_str));
+            for script in scripts {
+                Self::script_runner(script.as_os_str(), &args, &env).await
+            }
+        }
+    }
+    pub async fn handle_event(&self, event: &EventMessage) {
+        match event {
+            EventMessage::StateChange(change) => self.send_state_change(change).await,
+        }
+    }
+    async fn event_loop(mut self) {
+        info!("ScriptHookSink started");
+        while let Some(event) = self.rx_channel.recv().await {
+            debug!("ScriptHookSink got event {:?}", event);
+            self.handle_event(&event).await
+        }
+    }
+}

src/lib.rs

@@ -0,0 +1,75 @@
+pub mod bfd;
+pub mod control;
+pub mod events;
+
+use std::{
+    fmt::{self, Display},
+    net::IpAddr,
+    time::Instant,
+};
+
+use log::debug;
+use nix::sys::socket::{getsockopt, setsockopt, sockopt};
+use tokio::net::UdpSocket;
+
+use crate::bfd::*;
+
+#[derive(Debug)]
+pub struct BfdSessionStats {
+    pub local_ip: IpAddr,
+    pub remote_ip: IpAddr,
+    pub local_discr: BfdDiscriminator,
+    pub remote_discr: BfdDiscriminator,
+    pub state: BfdState,
+    pub last_diag: BfdDiagnostic,
+    pub control_packets_rx: u64,
+    pub control_packets_tx: u64,
+    pub last_change: Instant,
+    pub detect_time: BfdInterval,
+    pub base_interval: BfdInterval,
+}
+impl BfdSessionStats {
+    pub fn with_base_interval(mut self, base_interval: BfdInterval) -> Self {
+        self.base_interval = base_interval;
+        self
+    }
+}
+impl Display for BfdSessionStats {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        writeln!(
+            f,
+            "{:<20} {:<9} {:>6} {:>6}",
+            self.remote_ip, self.state, self.control_packets_rx, self.control_packets_tx
+        )?;
+        write!(
+            f,
+            "  LocalDiscr:{} RemoteDiscr:{} DetectTime: {} TxTime: {} Diag:{} Last: {}s",
+            self.local_discr,
+            self.remote_discr,
+            self.detect_time,
+            self.base_interval,
+            self.last_diag,
+            Instant::now().duration_since(self.last_change).as_secs()
+        )
+    }
+}
+
+pub fn set_ttl_or_hop_limit(sock: &UdpSocket, hop_limit: u8) -> Result<(), std::io::Error> {
+    let addr = sock.local_addr()?;
+    if addr.is_ipv4() {
+        debug!("IPv4 socket, setting ttl {}", hop_limit as u32);
+        sock.set_ttl(hop_limit as u32)
+    } else if addr.is_ipv6() {
+        debug!("IPv6 socket, setting hop limit {}", hop_limit as i32);
+        let i32_hop_limit = hop_limit as i32;
+        if let Err(e) = setsockopt(sock, sockopt::Ipv6Ttl, &i32_hop_limit) {
+            Err(std::io::Error::from_raw_os_error(e as i32))
+        } else {
+            let res = getsockopt(sock, sockopt::Ipv6Ttl)?;
+            debug!("Got {} after setting {}", res, i32_hop_limit);
+            Ok(())
+        }
+    } else { 
+        panic!("UdpSocket with no address family ?!")
+    }
+}